# Patent

## Title
Authentication in an audio/visual system having multiple signaling paths

## Abstract

A method and structure for authentication in a system having devices capable of communicating via multiple signal paths. Authentication is carried out between first and second devices. A first device communicates with a second device over a first data signaling path of an interface between the first and second devices in a first portion of an authentication process. A second device communicates with the first device over a second data signaling path of the interface between the first and second devices in a second portion of the authentication process.

## Background
CROSS REFERENCE TO RELATED APPLICATIONS
This application is related to application Ser. No. 11/695,359, entitled “METHOD AND APPARATUS TO SPEED TRANSMISSION OF CEC COMMANDS”, filed even date herewith, which is hereby incorporated by reference.
COPYRIGHT NOTICE
A portion of the disclosure of this patent document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.
FIELD OF THE INVENTION
The invention relates generally to digital audio/visual communications. More particularly, the invention relates to a method and apparatus for authentication of communications in digital communication systems having multiple input devices employing multiple interfaces.
BACKGROUND
In today's digital audio/visual (A/V) systems, it is quite common for a device to be in communication with multiple other devices and to accordingly have a number of inputs in order to accommodate communications with the multiple other devices. Accordingly, multiple data signaling paths may exist between multiple digital A/V devices, herein referred to as modules, which may include a set-top box (STB) or set-back box (SBB), a DVD player, a PC, a video game system, an A/V receiver, and a compatible digital audio and/or video monitor device, such as a television (TV) or a digital television (DTV) to facilitate communications between the multiple modules and a TV.
The data signal paths provided by multiple interfaces between devices of an A/V system can and do vary in protocol and number. For example, a TV or DTV may communicate via multiple data signaling paths to the various modules connected to it, including High Definition Multimedia Interface (HDMI®) CEC, HDMI I2C, HDMI Video, Universal Serial Bus (USB), Ethernet (wired or wireless), IEEE 1394 (so-called firewireTM or i-linkTM), Bluetooth, and RF. HDMI®, for instance, is a digital audio/visual connector interface capable of transmitting uncompressed and compressed streams, and can provide an interface between any compatible digital audio/video (A/V) source device, or module, and a compatible digital audio and/or video monitor device, such as a TV. Using HDMI, audio, visual, status and control information may be transmitted via one cable in the system. Consumer Electronic Control (CEC) is a protocol used to control devices that are attached using HDMI. CEC features, as may be defined from time to time in the CEC Specification, include routing control, standby, system information, and feature abort.
There can be problems attendant with such input/output devices communicating with multiple other devices (modules) via various signaling paths or interfaces. One concern is that of mis-wiring. In the case of a TV in communication with potentially many different modules, each module can use a variety of signaling path interfaces to communicate with the TV, including HDMI CEC, HDMI Video, HDMI I2C, and USB2, for example, and mis-wiring is a common concern when there are many ways to connect the modules to the TV. For instance, a user of the system can plug-in module, such as a STB or SBB using a HDMI #1 connector but then use a USB2 #2 connector. If multiple modules are used, this situation may confuse the TV.
In addition, there is also the concern of hackers trying to gain unauthorized access to the communication interface(s) between system devices. The greater the number of modules attached to the TV, for instance, the greater the number of paths that may be attacked and thus the greater the concern.



BRIEF DESCRIPTION OF THE DRAWINGS
The features of the invention believed to be novel are set forth with particularity in the appended claims. The invention itself however, both as to organization and method of operation, together with objects and advantages thereof, may be best understood by reference to the following detailed description of the invention, which describes certain exemplary embodiments of the invention, taken in conjunction with the accompanying drawings in which:
FIG. 1 is a system block diagram of a system using a set-top box.
FIG. 2 is a functional block diagram of a digital set-top box suitable for use with the present invention.
FIG. 3 is a HDMI system block diagram.
FIG. 4 illustrates a CEC command structure.
FIG. 5 is a block diagram of an exemplary system capable of enhanced transmission of CEC commands in accordance with certain embodiments.
FIG. 6 is a block diagram of an exemplary system capable of transmission of CEC commands using an enhanced HDMI interface in accordance with certain embodiments.
FIG. 7 is a block diagram of an exemplary system capable of transmission of CEC commands using an enhanced USB interface in accordance with certain embodiments.
FIG. 8 is a block diagram of an exemplary TV and multiple module system.
FIG. 9 is a block diagram of an exemplary system having multiple input devices and multiple data signaling paths or interfaces.
FIG. 10 is a sequence diagram illustrating transition of CEC command transmission from a first to a second interface in accordance with certain embodiments.



Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
DETAILED DESCRIPTION
While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail specific embodiments, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. In the description below, like reference numerals are used to describe the same, similar or corresponding parts in the several views of the drawings.
In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
Reference throughout this document to “one embodiment”, “certain embodiments”, “an embodiment” or similar terms means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of such phrases or in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments without limitation.
The term “or” as used herein is to be interpreted as an inclusive or meaning any one or any combination. Therefore, “A, B or C” means “any of the following: A; B; C; A and B; A and C; B and C; A, B and C”. An exception to this definition will occur only when a combination of elements, functions, steps or acts are in some way inherently mutually exclusive.
It will be appreciated that embodiments of the invention described herein may be comprised of one or more conventional processors and unique stored program instructions that control the one or more processors to implement, in conjunction with certain non-processor circuits, some, most, or all of the functions described herein. The non-processor circuits may include, but are not limited to, a radio receiver, a radio transmitter, signal drivers, clock circuits, power source circuits, and user input devices. As such, these functions may be interpreted as a method to perform functions such as acquisition of a new policy in accordance with certain embodiments consistent with the present invention. Alternatively, some or all functions could be implemented by a state machine that has no stored program instructions, or in one or more application specific integrated circuits (ASICs), in which each function or some combinations of certain of the functions are implemented as custom logic. Of course, a combination of the two approaches could be used. Thus, methods and means for these functions have been described herein. Further, it is expected that one of ordinary skill, notwithstanding possibly significant effort and many design choices motivated by, for example, available time, current technology, and economic considerations, when guided by the concepts and principles disclosed herein will be readily capable of generating such software instructions and programs and ICs with minimal experimentation.
A method and structure operable for authenticating, in a system having devices capable of communicating via multiple signal paths, one or more of the devices is described. A method includes a first device communicating with a second device over a first data signaling path of an interface between the first and second devices in a first portion of an authentication process; and the second device communicating with the first device over a second data signaling path of the interface between first and second devices in a second portion of the authentication process. Prior to the first device communicating with the second device over the first data signaling path, it can be confirmed that the first and second data signaling paths are operable. Authentication can be used to verify that a device is permitted to be in communication with another device, such as that a module is authorized to be in communication with a TV. For instance, a module will not be authenticated for use with a TV if a key returned from the module to the TV over the first data signaling path in the first portion of the authentication process does not reflect a physical address provided by the module to the TV over the second data signaling path in the second portion of the authentication process. Similarly, a module will not be authenticated if a vendor identification of the module received by the TV over the first data signaling path of the interface is not expected by the TV. A physical address is a unique number that the module gets from the TV; therefore, the TV can use it to distinguish the module from other devices.
An audio/visual (A/V) system compatible with various embodiments described herein is operable to employ multiple signal paths in communications between devices of the system. The system may have a television having a first connector operable for connecting said television to a first communication protocol and a second connector operable for connecting said television to a second communication protocol; and a module having a first module connector operable for connecting said module to the first communication protocol and a second module connector operable for connecting said module to the second communication protocol. In an authentication process between the television and the module, the television and the module are operable to communicate over a first data signaling path of a communication interface in accordance with the first communication protocol and over a second data signaling path of the communication interface in accordance with the second communication protocol. There may be multiple modules in the system, such as a second module having a third module connector corresponding to the first communication protocol and a fourth module connector corresponding to the second communication protocol. In an authentication process between the television and the second module, the television and the second module are operable to communicate over a third data signaling path of a second communication interface in accordance with the first communication protocol and over a fourth data signaling path of the second communication interface in accordance with the second communication protocol. Furthermore, the second module may be operable to communicate using a different communication protocol, in which case the television has a third connector corresponding to a third communication protocol; and the second module has a third module connector corresponding to the first communication protocol and a fourth module connector corresponding to the third communication protocol. The second module would be able to communicate with the television in an authentication process over a third data signaling path of a second communication interface in accordance with the first communication protocol and over a fourth data signaling path of the second communication interface in accordance with the third communication protocol.
A module itself in accordance with various embodiments has a programmed processor; a software segment running on the programmed processor; a user interface software segment running on the programmed processor that receives user commands using the software segment; a first module connector operable for connecting said module to a first communication protocol; and a second module connector operable for connecting said module to a second communication protocol. The software segment may be an Internet video player, such as Microsoft's Windows media player, a DVD player, an Internet browser, etc. The programmed processor controls operation of the module so that when the first module connector is coupled to a first data signaling path of an interface, the module is operable to communicate over the first data signaling path of the communication interface in accordance with the first communication protocol; when the second module connector is coupled to a second data signaling path of an interface, the module is operable to communicate over the second data signaling path of the communication interface in accordance with the second communication protocol. In an authentication process between a television and the module, the television and the module are operable to communicate over a first data signaling path of a communication interface in accordance with the first communication protocol and over a second data signaling path of the communication interface in accordance with the second communication protocol. The module is one or more of a set-top box, a set-back box, a DVD player, a PC, a video game system, and an A/V receiver.
Referring to FIG. 1, a block diagram for an exemplary interactive cable or satellite television (TV) system 100 is shown. The system 100 includes, at a head end of the service provider 10, a media server 12 for providing, on demand, movies and other programming obtained from a media database 14. The media server 12 might also provide additional content such as interviews with the actors, games, advertisements, available merchandise, associated Web pages, interactive games and other related content. The system 100 also includes an electronic programming guide (EPG) server 16 and a program listing database 18 for generating an EPG. Set-top box 22 can generally provide for bidirectional communication over a transmission medium 20 in the case of a cable STB 22. In other embodiments, bidirectional communication can be effected using asymmetrical communication techniques possibly using dual communication media—one for the uplink and one for the downlink. In any event, the STB 22 can have its own Universal Resource Locator (URL) or IP address or other unique identifier assigned thereto to provide for addressability by the head end and users of the Internet.
The media server 12 and EPG server 16 are operatively coupled by transmission medium 20 to a set-top box (STB) 22. The transmission medium 20 may include, for example, a conventional coaxial cable network, a fiber optic cable network, telephone system, twisted pair, a satellite communication system, a radio frequency (RF) system, a microwave system, other wireless systems, a combination of wired and wireless systems or any of a variety of known electronic transmission mediums. In the case of a cable television network, transmission medium 20 is commonly realized at the subscriber's premises as a coaxial cable that is connected to a suitable cable connector at the rear panel of the STB 22. In the case of a Direct Satellite System (DSS), the STB 22 is often referred to as an Integrated Receiver Decoder (IRD). In the case of a DSS system, the transmission medium is a satellite transmission at an appropriate microwave band. Such transmissions are typically received by a satellite dish antenna with an integral Low Noise Block (LNB) that serves as a down-converter to convert the signal to a lower frequency for processing by the STB 22.
The exemplary system 100 further includes a TV 24, such as a digital television, having a display 26 for displaying programming, an EPG, etc. The STB 22 may be coupled to the TV 24 and various other audio/visual devices 27 (such as audio systems, Personal Video Recorders (PVRs), Video Tape Recorders (VTRs), Video Cassette Recorders (VCRs) and the like), storage devices (e.g., hard disc drives) and Internet Appliances 28 (such as email devices, home appliances, storage devices, network devices, and other Internet Enabled Appliances) by an appropriate interface 30, which can be any suitable analog or digital interface. In one embodiment, interface 30 conforms to an interface standard such as the Institute of Electrical and Electronics Engineers (IEEE) 1394 standard, but could also be wholly or partially supported by a DVI interface (Digital Visual Interface-Digital Display Working Group, www.ddwg.org), HDMI or other suitable interface.
The STB 22 may include a central processing unit (CPU) such as a microprocessor and memory such as Random Access Memory (RAM), Read Only Memory (ROM), flash memory, mass storage such as a hard disc drive, floppy disc drive, optical disc drive or may accommodate other electronic storage media, etc. Such memory and storage media is suitable for storing data as well as instructions for programmed processes for execution on the CPU, as will be discussed later. Information and programs stored on the electronic storage media or memory may also be transported over any suitable transmission medium such as that illustrated as 20. STB 22 may include circuitry suitable for audio decoding and processing, the decoding of video data compressed in accordance with a compression standard such as the Motion Pictures Experts Group (MPEG) standard and other processing to form a controller or central hub. Alternatively, components of the STB 22 may be incorporated into the TV 24 itself, thus eliminating the STB 22. Further, a computer having a tuner device and modem may be equivalently substituted for the TV 24 and STB 22.
By way of example, the STB 22 may be coupled to devices such as a personal computer, video cassette recorder, camcorder, digital camera, personal digital assistant and other audio/visual or Internet related devices. In addition, a data transport architecture, such as that set forth by an industry group which includes Sony Corporation and known as the Home Audio-Video Interoperability (HAVi) architecture may be utilized to enable interoperability among devices on a network regardless of the manufacturer of the device. This forms a home network system wherein electronic devices and Internet appliances are compatible with each other. The STB 22 runs an operating system suitable for a home network system such as Sony Corporation's AperiosTM real time operating system. Other operating systems could also be used.
The STB 22 includes an infrared (IR) receiver 34 for receiving IR signals from an input device such as remote control or commander 36. Alternatively, it is noted that many other control communication methods may be utilized besides IR, such as wired or wireless radio frequency, etc. In addition, it can be readily appreciated that the input device 36 may be any device suitable for controlling the STB 22 such as a remote control or commander, personal digital assistant, laptop computer, keyboard or computer mouse. In addition, an input device in the form of a control panel located on the TV 24 or the STB 22 can be provided.
The STB 22 may also be coupled to an independent service provider (ISP) host 38 by a suitable connection including dial-up connections, DSL (Digital Subscriber Line) or the same transmission medium 20 described above (e.g., using a cable modem) to, thus, provide access to services and content from the ISP and the Internet. The ISP host 38 provides various content to the user that is obtained from a content database 52. STB 22 may also be used as an Internet access device to obtain information and content from remote servers such as remote server 48 via the Internet 44 using host 38 operating as an Internet portal, for example. In certain satellite STB environments, the data can be downloaded at very high speed from a satellite link, with asymmetrical upload speed from the set-top box provided via a dial-up or DSL connection.
While the arrangement illustrated in FIG. 1 shows a plurality of servers and databases depicted as independent devices, any one or more of the servers can operate as server software residing on a single computer. Moreover, although not explicitly illustrated, the servers may operate in a coordinated manner under centralized or distributed control to provide multiple services as a Multiple Service Operator (MSO) in a known manner. Additionally, the services provided by the servers shown in FIG. 1 may actually reside in other locations, but from the perspective of the user of STB 22, the service provider 10 serves as a portal to the services shown. Those skilled in the art will appreciate that the illustration of FIG. 1 represents a simplified depiction of a cable system configuration shown simply as service provider 10. The actual configuration of the service provider's equipment is more likely to follow a configuration defined by the CableLabs OpenCableTM specification. The simplified illustration shown is intended to simplify the discussion of the service provider 10's operation without unnecessarily burdening the discussion with architectural details that will be evident to those skilled in the art. Those details can be found in the publicly available CableLabs OpenCableTM specification or in the text “OpenCable Architecture (Fundamentals)” by Michael Adams, Cisco Press, November 1999.
Referring now to FIG. 2, a typical system configuration for a digital set-top box 22 is illustrated. In this exemplary set-top box, the transmission medium 20, such as a coaxial cable, is coupled by a suitable interface through a diplexer 102 to an in-band tuner 104. Tuner 104 may, for example, include a broadcast in-band tuner for receiving video content. An out-of-band (OOB) tuner 105 is provided for receiving data transmissions, including ATM formatted SI data. A return path through diplexer 102 provides an OOB return path for outbound data (destined for example for the head end). A separate tuner (not shown) may be provided to receive conventional RF broadcast television channels. Modulated information formatted, for example, as MPEG-2 information is then demodulated at a demodulator 106. The demodulated information at the output of demodulator 106 is provided to a demultiplexer and descrambler circuit 110 where the information is separated into discrete channels of programming. The programming is divided into packets, each packet bearing an identifier called a Packet ID (PID) that identifies the packet as containing a particular type of data (e.g., audio, video, data). The demodulator and descrambler circuit 110 also decrypts encrypted information in accordance with a decryption algorithm to prevent unauthorized access to programming content, for example.
Audio packets from the demultiplexer 110 (those identified with an audio PID) are decrypted and forwarded to an audio decoder 114 where they may be converted to analog audio to drive a speaker system (e.g., stereo or home theater multiple channel audio systems) or other audio system 116 (e.g., stereo or home theater multiple channel amplifier and speaker systems) or may simply provide decoded audio out at 118. Video packets from the demultiplexer 110 (those identified with a video PID) are decrypted and forwarded to a video decoder 122. In a similar manner, data packets from the demultiplexer 110 (those identified with a data PID) are decrypted and forwarded to a data decoder 126.
Decoded data packets from data decoder 126 are sent to the set-top box's computer system via the system bus 130. A central processing unit (CPU) 132 can thus access the decoded data from data decoder 126 via the system bus 130. Video data decoded by video decoder 122 is passed to a graphics processor 136, which is a computer optimized to processes graphics information rapidly. Graphics processor 136 is particularly useful in processing graphics intensive data associated with Internet browsing, gaming and multimedia applications such as those associated with MHEG (Multimedia and Hypermedia information coding Experts Group) set-top box applications. It should be noted, however, that the function of graphics processor 136 may be unnecessary in some set-top box designs having lower capabilities, and the function of the graphics processor 136 may be handled by the CPU 132 in some applications where the decoded video is passed directly from the demultiplexer 110 to a video encoder. Graphics processor 136 is also coupled to the system bus 130 and operates under the control of CPU 132.
Many set-top boxes such as STB 22 may incorporate a smart card reader 140 for communicating with a so called “smart card,” often serving as a Conditional Access Module (CAM). The CAM typically includes a central processor unit (CPU) of its own along with associated RAM and ROM memory. Smart card reader 140 is used to couple the system bus of STB 22 to the smart card serving as a CAM (not shown). Such smart card based CAMs are conventionally utilized for authentication of the user and authentication of transactions carried out by the user as well as authorization of services and storage of authorized cryptography keys. For example, the CAM can be used to provide the key for decoding incoming cryptographic data for content that the CAM determines the user is authorized to receive.
STB 22 can operate in a bidirectional communication mode so that data and other information can be transmitted not only from the system's head end to the end user, or from a service provider to the end user of the STB 22, but also, from the end user upstream using an out-of-band channel. In one embodiment, such data passes through the system bus 130 to a modulator 144 through the diplexer 102 and out through the transmission medium 20. This capability is used to provide a mechanism for the STB 22 and/or its user to send information to the head end (e.g., service requests or changes, registration information, etc.) as well as to provide fast outbound communication with the Internet or other services provided at the head end to the end user.
Set-top box 22 may include any of a plurality of I/O (Input/Output) interfaces represented by I/O interfaces 146 that permit interconnection of I/O devices to the set-top box 22. By way of example, and not limitation, a serial RS-232 port 150 can be provided to enable interconnection to any suitable serial device supported by the STB 22's internal software. Similarly, communication with appropriately compatible devices can be provided via an Ethernet port 152 (wired or wireless), a USB (Universal Serial Bus) port 154, an IEEE 1394 (so-called firewireTM or i-linkTM) or IEEE 1394 wide port 156, S-video port 158 or infrared port 160, or Bluetooth. Such interfaces can be utilized to interconnect the STB 22 with any of a variety of accessory devices such as storage devices, audio/visual devices 27, gaming devices (not shown), Internet Appliances 28, etc.
I/O interfaces 146 can include a modem (be it dial-up, cable, DSL or other technology modem) having a modem port 162 to facilitate high speed or alternative access to the Internet or other data communication functions. In one preferred embodiment, modem port 162 is that of a DOCSIS (Data Over Cable System Interface Specification) cable modem to facilitate high speed network access over a cable system, and port 162 is appropriately coupled to the transmission medium 20 embodied as a coaxial cable. Thus, the STB 22 can carry out bidirectional communication via the DOCSIS cable modem with the STB 22 being identified by a unique IP address. The DOCSIS specification is publicly available.
A PS/2 or other keyboard/mouse/joystick interface such as 164 can be provided to permit ease of data entry to the STB 22. Such inputs provide the user with the ability to easily enter data and/or navigate using pointing devices. Pointing devices such as a mouse or joystick may be used in gaming applications.
Of course, STB 22 also may incorporate basic video outputs 166 that can be used for direct connection to a television set such as 24 instead of (or in addition to) an IEEE 1394 connection such as that illustrated as 30. In one embodiment, Video output 166 can provide composite video formatted as NTSC (National Television System Committee) video. In some embodiments, the video output 166 can be provided by a direct connection to the graphics processor 136 or the demultiplexer/descrambler 110 rather than passing through the system bus 130 as illustrated in the exemplary block diagram. S-Video signals from output 158 can be similarly provided without passing through the system bus 130 if desired in other embodiments.
The infrared port 160 can be embodied as an infrared receiver 34 as illustrated in FIG. 1, to receive commands from an infrared remote control 36, infrared keyboard or other infrared control device. Although not explicitly shown, front panel controls may be used in some embodiments to directly control the operation of the STB 22 through a front panel control interface as one of interfaces 146. Selected interfaces such as those described above and others can be provided in STB 22 in various combinations as required or desired.
STB 22 will more commonly, as time goes on, include a disc drive interface 170 and disc drive mass storage 172 for user storage of content and data as well as providing storage of programs operating on CPU 132. STB 22 may also include floppy disc drives, CD ROM drives, CD R/W drives, DVD drives, etc. CPU 132, in order to operate as a computer, is coupled through the system bus 130 (or through a multiple bus architecture) to memory 176. Memory 176 may include a combination any suitable memory technology including Random Access Memory (RAM), Read Only Memory (ROM), Flash memory, Electrically Erasable Programmable Read Only Memory (EEPROM), etc.
While the above exemplary system including STB 22 is illustrative of the basic components of a digital set-top box suitable for use with the present invention, the architecture shown should not be considered limiting since many variations of the hardware configuration are possible without departing from the present invention. The present invention could, for example, also be implemented in more advanced architectures such as that disclosed in U.S. patent application Ser. No. 09/473,625, filed Dec. 29, 1999, entitled “Internet Set-Top Box Having and In-Band Tuner and Cable Modem” and issued as U.S. Pat. No. 6,757,909 on Jun. 29, 2004 to Jun Maruo and Atsushi Kagami.
This patent describes a set-top box using a multiple bus architecture with a high level of encryption between components for added security. This application is hereby incorporated by reference as though disclosed fully herein.
In general, during operation of the STB 22, an appropriate operating system 180 such as, for example, Sony Corporation's AperiosTM real time operating system is loaded into, or is permanently stored in, active memory along with the appropriate drivers for communication with the various interfaces. In other embodiments, other operating systems such as Microsoft Corporation's Windows CETM could be used without departing from the present invention. Along with the operating system and associated drivers, the STB 22 usually operates using browser software 182 in active memory or may permanently reside in ROM, EEPROM or Flash memory, for example. The browser software 182 typically operates as the mechanism for viewing not only web pages on the Internet, but also serves as the mechanism for viewing an Electronic Program Guide (EPG) formatted as an HTML document. The browser 182 can also provide the mechanism for viewing normal programming (wherein normal programming is viewed as an HTML video window—often occupying the entire area of screen 26).
STB software architectures vary depending upon the operating system. However, in general, all such architectures generally include, at the lowest layer, various hardware interface layers. Next is an operating system layer as previously described. The software architectures of modern STB have generally evolved to include a next layer referred to as “middleware.” Such middleware permits applications to run on multiple platforms with little regard for the actual operating system in place. Middleware standards are still evolving at this writing, but are commonly based upon Javascript and HTML (hypertext Markup Language) virtual machines. At the top layer is the application layer where user applications and the like reside (e.g., browsing, email, EPG, Video On Demand (VOD), rich multimedia applications, pay per view, etc.). The current invention can be utilized with any suitable set-top box software and hardware architecture. FIG. 3 references an exemplary HDMI System Block Diagram, said system transmitting CEC commands over a single cable. The HDMI-compatible device that is transmitting information may be referred to as a HDMI source device, while the HDMI-compatible device receiving the transmitted information is referred to as a HDMI sink device. It can be seen that audio, visual, control, status and CEC control information may be transmitted via one cable in the system. Of course, in a bidirectional system in which information is flowing both directions between various HDMI-compatible devices, such as between a TV and a module, like a STB or SBB, each device will have an HDMI transmitter and HDMI receiver and may be referred to as a source or sink device depending upon whether it is transmitting or receiving information.
HDMI 1.2a, released in December 2005 supports CEC features, command sets, and CEC compliance tests. Using a single cable, CEC control allows a user to control all HDMI devices with a remote control or commander user interface, including powering on or off connected devices, commands initiated by devices to other devices. It thus solves the problem of “too many remote controls.” For instance, a user can press play on one HDMI device, such as a DVD, and operation of CEC commands causes the A/V receiver to automatically turn on and switch to the correct input, which in turn automatically turns on the TV, which automatically switches to the correct input received from the A/V receiver; such is an example of “one-touch play.”
CEC features, as may be defined from time to time in the CEC Specification, Section 3.1, include one touch play, system audio control, etc. Other, optional features may include one touch recording, deck control, tuner control, On Screen Display (OSD) display, OSD name transfer, device menu control, RC pass-through, power status and vendor-specific commands (such as a vendor remote command). CEC control commands that may be particularly of interest in the communication between a STB (SBB) and TV may include the following: request active source, image view on, text view on, standby, give physical address, get menu language, polling message, report physical address, set menu language, device vendor ID, give device ID, user remote control pressed, user control released, set OSD string, give OSD name, set OSD name, give device power status, report power status, feature abort.
Of course, it is understood that the HDMI specification continues to mature, new CEC commands may be expected to be added from time to time as developed. A standard CEC command structure is illustrated in FIG. 4. This structure may remain the same to provide for back-ward compatibility.
As has been described the standard HDMI CEC signal path from device to device is unacceptably slow. This original CEC signal path of the HDMI connector is half duplex and slow, resulting in a sluggish remote control or commander user interface. It is known that certain interfaces are much faster than the standard CEC interface, with USB, USB2 for instance, being able to send and receive information in less time than it takes to just transmit in CEC.
In accordance with certain embodiments, alternate signaling paths are provided for transmission of CEC commands between HDMI-compatible devices, such as between a set-top box (STB), or set-back box (SBB), and a television (TV) or digital television (DTV) in order to provide faster signaling and a better user experience. Whereas the original CEC signal path of the HDMI connector is half duplex and slow, resulting in a sluggish remote control or command user interface, alternate signaling paths are relatively faster and thus can provide a better user experience. Various embodiments in which faster signaling may be achieved will be described, and include different signaling paths that are used instead of or in addition to the normal HDMI CEC connector data path.
This is illustrated in FIG. 5, in which an exemplary system diagram, focusing on the transmission of CEC command information between a first HDMI-compatible device, such as a television, and a second HDMI-compatible device, such as a STB or SBB, is shown. In accordance with embodiments of the invention, since it is desirable to transmit CEC command information between devices using a faster, alternate data signal path, there are two communication interfaces or data paths shown. Both Interfaces are capable of transmitting CEC commands but may have differing speed characteristics. Interface 1 may be considered the normal HDMI CEC signal path that is unacceptably slow while Interface 2 is the enhanced, faster data transmission path. As will be described, Interface 2 may rely upon a faster signal path through the HDMI connector, as illustrated in FIG. 6 or it may be based upon another protocol entirely such as USB, as shown in FIG. 7. Moreover, Interface 2 may be used instead of, or in addition to, the original HDMI CEC Interface 1. This is illustrated by the dashed “X” on the standard CEC interface of FIGS. 6 and 7, for example, to indicate that the use of the original, slower standard CEC interface may or may not continue to be used.
Referring again to FIG. 6, the alternate, enhanced data signaling path for transmitting CEC commands between devices envisions an alternate signaling path within the HDMI connector itself. Since a HDMI interface will continue to be used, it may not be necessary to connect a separate cable to facilitate these embodiments. In a first embodiment, the I2C data channel of the HDMI connector is used as an alternate path. I2C is a multi-master serial computer bus that may be used to attach peripherals to a motherboard or embedded system and may provide a readily available interface solution for this purpose. I2C may be used in regular or high speed mode in the HDMI connector. As an example, this interface may be used for a proposed High-bandwidth Digital Content Protection (HDCP) key digital rights management (DRM) transaction adapted to transfer CEC traffic. In this embodiment, the original CEC path, shown as the Standard CEC Interface in the figure, may be disabled.
In a second embodiment, an alternate, faster signaling path within the HDMI interface uses a reserved PIN in the HDMI connector, and may be used independently of or in addition to the CEC path. Version A of the HDMI connector specifies that Pin 14, for instance, is a reserved pin. In this instance, the reserved PIN in the HDMI connector may be used as another half-duplex signaling path, and thus this interface may be used independently of or in addition to the CEC path. The set-back module (SBB) and TV can recognize that they have this signaling capability and can switch to using this additional path through the reserved PIN. In this embodiment, the standard CEC interface path may be optionally used. If both interfaces are used, a much improved speed for transmission of CEC commands between the devices may be realized.
In a third embodiment, USB is used as an alternate path for CEC signaling and, as it is not HDMI based, the system will require the use of two cables or interfaces, one HDMI and the other USB. USB is faster than the original CEC path and can thus be used to increase responsiveness to CEC remote control commands. In this embodiment, the original CEC path may be disabled. The same data format used for the CEC interface is used over the USB interface. An exemplary CEC message format might be:













32 bits
length


16 bits
command_id


32 bits
sequence_num


128 bits 
CEC_frame









Where length is the length of the message, command_ID is the ID number that can be used to distinguish the CEC command over USB from other commands over USB, and sequence num is the number that is numbered sequentially when the command over USB is issued.

    CEC Frame:
    CEC_frame[0] header block (§6 of CEC spec)
    CEC_frame[1] Data Block (opcode block)
    CEC_frame[2-15] Data Block2 (operand blocks)

Note that EOM and ACK as defined in the CEC specification may be omitted when the CEC command is sent over USB as the other end of the message or an acknowledgement method can be used.



USB, including USB2, is a useful interface for sending a variety of information between devices. For instance, TCIP is established over USB; thus, CEC commands are just one of the commands sent over the USB.
The use of the USB as an alternate path or interface for transmitting CEC commands between two devices requires the use of two physical cables, as previously noted.
The approach chosen can enhance security, making sure that the TV is talking to an approved module, a particular concern when multiple modules might be attached to the TV. Not only may the approach taken enhance security; consumer protection may be enhanced as well. A module can interface to the television using HDMI and USB. In an exemplary embodiment, a television might have as many as four HDMI and USB connectors and it is not uncommon for a user to not properly connect the equipment. Moreover, multiple modules might be attached to the TV.
The ability of a module to interface to a TV using multiple protocols, whether they be HDMI, USB, or otherwise, provides clear advantages. The protocol may be started with a certain protocol, such as either HDMI or USB2, and then continued and/or completed with the other protocol. However, there are security and customer concerns with multiple input systems. Obviously the greater the number of modules attached to the TV, the greater the concern about hacking. In addition to this security concern, consider that a mis-wiring has occurred, a common occurrence when there are many possible ways to connect components such as when multiple modules might be attached to a TV.
Refer to FIG. 8, in which an exemplary system having a TV and two module devices Device A and Device B is illustrated. It is necessary to determine whether the HDMI A and USB A interface signaling paths are connected to Device A. If Device A sends the information that is acquired from interface HDMI A, then the TV can determine that interface USB A is connected to Device A. The physical address is the information that is acquired from the HDMI connection, HDMI A. Suppose that Device A gets physical address 1.0.0.0. from HDMI A connection and sends that address 1.0.0.0. over USB A to the TV. The TV can know that the USB A is connected to Device A. Similarly, the Device B gets physical address 2.0.0.0. from HDMI B connection and sends 2.0.0.0. from the HDMI B connection and sends 1.0.0.0. over interface USB B. The TV knows that the USB B is connected to Device B.
It can be seen that this form of authentication, using physical addresses, overcomes concerns associated with multiple device and multiple interface systems. Both security and consumer protection concerns are addressed.
In order to address these concerns the migration or switching of transmission of a protocol such as CEC commands from the CEC interface to an alternative physical layer or interface such as a reserved pin, I2C bus, or even USB, would occur after authentication of the two devices. Authentication of a device, such as a module, ensures that it is permitted to be talking to the other device of interest, such as the TV. As it is envisioned that a TV may not know which devices or modules are authorized to interface with it, authentication addresses this issue. It will point out problems such as there not being physical connection between the devices via the appropriate cable(s). As it is entirely conceivable that a TV may not know whether a module is connected to it, authentication discovers such problems so they can be remedied. Moreover, authentication provides a mechanism of exercising control of which devices will be authorized to use the communication path. Non-authorized devices may be precluded from operating in the transmission of CEC commands in the enhanced manner provided herein.
This would allow enhanced devices capable of starting transmission of a protocol using a first interface and then continuing or completing transmission of the protocol with a second interface to operate amongst non-enhanced devices. Once enhanced devices authenticate each other, they could negotiate the migration of the CEC commands to an alternative physical layer or interface that both devices have in common so that a faster, more efficient transmission of the protocol is realized.
Referring to the sequence diagram of FIG. 10, consider an example in which several commands that may be used for authentication purposes are illustrated. It is noted that not all the commands are necessary for authentication, as varying degrees of security may be desired. Moreover, the sequence diagram of the figure is in the context of switching from the standard HDMI CEC interface to an alternate USB interface.
However, it is understood that a similar might be undertaken for any of the other embodiments described herein. Finally, the sequence diagram illustrates a TV and a module, such as a STB or a SBB, as the two devices, but, again, it is within the scope of the present invention to undertake a similar authentication process for other HDMI-compatible devices.
The TV starts this sequence on bootup or when the TV recognizes that the device is attached. If the module is connected before the TV boot, the module will be recognized. At 1, the TV sends a polling message via the standard CEC interface to the module. At 2 and 3, the physical address and the logical addressing of the SBB are ascertained. At 4, the module can report its physical address to the TV and may provide this without first receiving the physical address of the TV at 5. If USB insertion is detected, then the TV gives its physical address to the module at 5, in preparation for possible migration from the standard CEC interface to a USB alternate interface. The exchange of physical addresses of the devices is one mechanism by which authentication may occur, as will be described.
At 6, the TV communicates its device vendor ID to the module via the standard CEC interface and the module provides this information to the TV, also over the standard CEC interface, at 7 as shown. This vendor ID information from the module, along with the physical address information given previously, is used to determine whether the module is permitted to communicate with the TV once the migration to the alternate USB interface is fade or even at all, although in this example it is not yet used. For instance, the TV, upon receiving a vendor ID from the module that does not match its own vendor ID, may make the determination that the module is not authenticated, because the TV will operate only with modules of a particular vendor, and at the right time, it will not engage in communication with the module over the alternate, faster interface.
At 8, 9, 10, and 11 OSD name and menu language information may be optionally exchanged, but such is not required for authentication to occur. 10, the get language command, for instance, may not occur in certain environments. However, such information can be used in the authentication process. For example, if the required OSD name, such as a Sony ID, is not returned by the module at 9, then the authentication would fail and the process stops.
Commands 12-21 center on vendor commands as shown. For 12, the version of the module is asked because if there is not acknowledge (ack) or feature abort returned from the module at 13, it may indicate that the device has only generic, standard CEC interface capability or it is not a SBB, as required, for instance, and thus the device cannot be authenticated in this example. Similar information might be gleaned from the device type inquires of 16, 17, and the capability inquires of 18, 19. Command 20 may not be asked if the USB bit is set on the report capability response received in 19. Furthermore, if the USB bit is not set on the report capability response of 19, then the inquiry could stop at 21.
At 22, all the device information exchanged between the TV and the module are collected for action. At 23 and 24, assuming that there have been no responses from the SBB module that disqualified if from authentication, then USB communication for both the module and for the TV, respectively, is setup as shown.
Following, setup for migration to the alternate, USB interface, bootup request and response is handled at 25 and 26. Encryption is provided such as, for example, by the SSL authentication at 27 and 28, whereby CEC commands thereafter are encrypted. Secure Sockets Layer (SSL) is just one example of a cryptographic protocol that can be used to secure communications on the Internet for data transfers for such things as web browsing, email, and instant messaging.
At 29 and 30, the TV requests a key from the module. At 31, this key is compared with the physical address earlier provided by the module at 4 and 5. If there is not a match, this may indicate that the module is not authorized for enhanced communication with the TV and authentication may accordingly be denied if there is a match, then transmission of CEC protocol commands from the first, slower CEC interface to the second, faster USB interface can proceed.
Alternately, the TV may have its own key and authentication may be performed by verifying that the key returned by each device to the other is the one expected. In a particular example, authentication is completed upon both devices returning the same key to each other; if the keys match, then transmission of CEC protocol commands from the first, slower CEC interface to the second, faster USB interface can proceed. If different keys are returned, then authentication between the two devices is rejected and transmission of the CEC commands will not be migrated to a better, faster interface. In certain embodiments, the TV will be the device to reject the migration if the keys differ, as is the case in this example in which the TV initiated the key inquiry to the SBB module. Authentication of a module can be achieved during boot up or when module discovery is initiated upon plugging in the module or when initiated by the user through the user interface (UI). The available modules and their types may be displayed on the screen of the TV user interface and only desired or authorized modules, such as a Sony SBB having the ability to switch from the CEC to an alternate interface, would be displayed on the screen for selection by the user.
It can be seen that the physical addresses and keys of the devices, TV and SBB in this example, may be used during authentication to verify these devices, one to the other, prior to commencing transmission of CEC commands over the CEC interface, which as previously mentioned, is a relatively slow interface.
Upon authentication, transmission of CEC commands between the devices will be effected over the faster, alternate path, USB in this example. For instance, in order to keep the quality of the user experience high with the TV, the TV does not filter remote control commands; instead, the TV forwards the remote control command to the device over the faster path.
The CEC interface cable may not be used during this time to transmit CEC commands, although the CEC cable can still be used to send other information, such as non-CEC commands, like application launch commands, and audio and visual information. In this case, the use of the standard CEC cable to transmit non-CEC commands allows the order in which such commands are transmitted to be known and therefore controlled.
It is to be noted that as part of authentication, additional information, such as a device identification number, may be used to verify that a device is an authorized device and thus control which devices have access to a faster communication path for CEC command protocol information. As a further example, upon initiating communication, a device might be requested to transmit an expected copyright notice across the USB interface. In order to start transmission of CEC commands via the USB path, the copyright notice must be present and verified.
Optionally, cryptography or encryption techniques, in addition to or instead of the SSL authentication discussed above, such as a Public Key approach, might be used to verify authorized devices and stop rogue devices. In both secret key and public key approaches, the TV device could send a random number, such as 128 bits, in the Auth_bytes command to the module. In the response, the module sends back an encrypted value in the Auth-status field. In the secret key case, there may be a shared secret value which is used to encrypt the random number. The size of the encrypted value is also 128 bits. The TV decrypts the value with the shared secret value to see if it matches the original clear value of the random number that was sent earlier.
In the public key case, the response also includes the certificate for the module. The TV may check the certificate for authenticity using a root Certificate Authority public key. (It can do this once and record the fact that it has seen this certificate before.) It then uses the public key in the certificate to decrypt the encrypted value. It then verifies that it got the same random value back. The certificate has it own length field so that the TV knows how to parse the Auth_status to get the certificate and then what is left is the encrypted random number. The random value may continually change so that this protocol is immune to replay attacks.
A note on authentication with regard to use of the known, standard CEC interface versus the use of USB as a faster, alternate signaling path for transmission of CEC commands is in order. Since with authentication, the devices (TV and module) authenticate each other at the beginning of communication, the data is sent to the trusted (authenticated) device. In this case, it is assumed that the data is transferred to the trusted device and data protection or encryption is not performed for the transaction over the CEC path. Since data over CEC is not sensitive, data is not encrypted over CEC.
Data over the USB interface, on the other hand, should be secured. This may be provided by a root certificate, for example, which will be issued by an authorized entity, that will be used to issue and sign TV and SBB's certificates. The certificate may be issued on a model basis, not per device. The certificate would be saved in a secure area of the device, and could be managed and/or configured by those having the proper clearance.
As was discussed in connection with the system of FIG. 8, devices can be connected to each other using multiple signaling paths; thus an interface between a first device and a second device may comprise multiple signaling paths, such as HDMI CEC, HDMI I2C, USB, etc. This facilitates communications of multiple modules to one TV for instance. There may therefore be multiple signaling paths or interfaces between a TV and the modules that wish to communicate with it. Therefore, in accordance with certain embodiments of the invention, authentication can occur between two devices using multiple signaling paths. Moreover, a combination of the various available signaling paths can be used in the authentication process. While the description has previously discussed the transmission of CEC commands using various protocols, authentication using multiple signaling paths may occur for transmission of any type of data, including CEC or other commands, audio, video, etc.
Consider the multiple signaling paths of FIG. 9 In this figure, a TV is shown in communication with three modules, Module 1, Module 2, and Module 3. In this example, although not required, an HDMI switch and a USB hub are used to facilitate communication between the TV and the various modules via HDMI signaling paths (shown as solid lines) and USB signaling paths (shown as dashed lines). Each of the data signal paths connects to the respective Modules and TV via the appropriate connector. So, for the example shown in the drawing, each Module has a USB connector and a HDMI connector. Hub devices are named according to the interface being used and must be supported by the TV. Examples of other hub devices include Ethernet switch, Ethernet hub, IEEE 1394 hub, RF splitter, composite video switch or selector, and component video switch or selector. Use of such hub devices, is a mechanism by which the number of connections available to the TV are increased even though the TV's physical port is limited. Often times, a TV has only limited number of physical connections in order to save costs. Furthermore, consider that a computer laptop has only one USB port, but you want to connect a USB mouse and USB memory to the laptop. In that case, it is necessary to hookup two or more USB port hubs to increase the number of available USB ports.
The multiple signaling paths that make up the interfaces between system devices of FIGS. 8 and 9 can be used to facilitate authentication and indeed enhance the robustness and security of authentication. A module(s) that is in communication with a TV, for example, may be authenticated over multiple signaling paths, just as a TV may be authenticated by one or more modules over multiple signaling paths. Such a module that is authenticating itself with the TV may use a first signaling path, such HDMI CEC, to send authentication data that is different from a second signaling path, such as USB, that is used by the TV to send data to the module. Authentication might be performed for all signaling paths between two devices, in order to ascertain that these paths exist. Authentication, then, may encompass authentication of devices as well as authentication of signaling paths.
Consider an example in which a TV and a module exchange random numbers to prevent replay attacks. The module can send information to the TV over the HDMI CEC signaling path while the TV could communication via the I2C signaling path. This is a unique communication involving two separate communication types and it is unlikely that it may be easily duplicated employing an interface having only a single signaling data path between the two devices.
Use of multiple interfaces in the authentication process makes it more difficult for a hacker to hack the communications between devices. A hacker will have more difficulty hacking into a system using multiple signaling paths as part of the authentication process. A simple module, incapable of supporting communication and authentication over multiple signaling paths, would not pass authentication described in context with multiple signaling path embodiments; for one thing, it would not likely contain the software required to control communication via multiple signaling paths. Thus, although a hacker may be able to probe a USB interface using a PC but not drive signals on the HDMI connector with a simple communication scheme, such will not be the case if the described method and structure if employed. Moreover, the concerns with mis-wiring that result from an increased number of modules attached to a TV, for instance, may be readily identified using multiple signal path authentication. In both security and wiring concerns described above, the ability of a module to interface to the TV using multiple interfaces provides a clear advantage. The protocol may be started with either interface, HDMI or USB2, for example, and then continued and/or completed with the other interface. Both security and consumer protection concerns are addressed.
In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.

## Claims

1. A method of authentication, comprising:
establishing a first bidirectional data signaling path between a first device of a plurality of devices and a second device of the plurality of devices, where the first bidirectional data signaling path uses a first set of compatible communication interfaces at the first and second the first devices;
the first device of the plurality of devices initiating a communication with the second device of the plurality of devices over the first data signaling path of using the first set of compatible communication interfaces between first and second devices;
the second device of the plurality of devices replying to the first device using the first bidirectional data signaling path over the first set of compatible communication interfaces between the first and second devices;
where the communication over the first data signaling path comprises an exchange of identifying information that identifies the second device to the first device as a first portion of an authentication process;
establishing a second bidirectional data signaling path between the first device and the second device, where the second bidirectional data signaling path uses a second set of compatible communication interfaces at the first and second devices;
the second device communicating with the first device over the second data signaling path of the second set of compatible bidirectional communication interfaces between first and second devices in a second portion of the authentication process that exchanges information to establish that the second device is permitted to be in communication with the first device thereby authenticating the second device to the first device.

2. The method of claim 1, where the establishing a first bidirectional data signaling path comprises confirming that the first bidirectional data signaling path of the first set of compatible communication interfaces between first and second devices of the plurality of devices is operable; and
where the establishing a second bidirectional data signaling path comprises confirming that the second bidirectional data signaling path of the interface between first and second devices is operable.

3. The method of claim 1, wherein said first device comprises a television and said second device comprises a module and authenticating the module only occurs if the module is permitted to be used with the television.

4. The method of claim 3, further comprising:
displaying the module to a user of the television for selection from a plurality of authenticated modules only if the module is authenticated.

5. The method of claim 4, where displaying to the user comprises displaying at least a part of a television menu on a television display.

6. The method of claim 3, further comprising:
not authenticating the module for use with the television if a key returned from the module to the TV over the first bidirectional data signaling path in the first portion of the authentication process does not reflect a physical address provided by the module to the television over the first bidirectional data signaling path in the first portion of the authentication process.

7. The method of claim 4, further comprising:
not authenticating the module for use with the television if a vendor identification of the module received by the television over the first data signaling path of the interface is not expected by the television.

8. A method for establishing transmission of Consumer Electronic Control (CEC) commands between a HDMI-compatible television and a HDMI-compatible module, comprising:
verifying that the module is permitted to transmit CEC commands back and forth with the television over both a standard bidirectional HDMI CEC interface and over an alternate bidirectional interface separate from the standard HDMI CEC interface, wherein verifying further comprises:
the module providing to the television over the alternate interface a module identifier that identifies the module to the television, wherein the module identifier is acquired by the module from the television over the standard HDMI CEC interface;
the television receiving the module identifier and using the module identifier to determine that the module is connected to the alternate interface;
the television providing to the module over the alternate interface the physical address of the television;
the television providing a vendor identifier of the television to the module over the standard HDMI CEC interface and the module providing the vendor identifier back to the television over the standard HDMI CEC interface, wherein receipt by the television of the module identifier and the vendor identifier verify to the television that the module is permitted to communicate with the television over the alternate interface;
the television and the module each migrating from the standard HDMI CEC interface to the alternate interface for communication of CEC commands over the alternate interface; and
the television and the module transmitting CEC commands over the alternate interface.

9. The method of claim 8, wherein the module providing the module identifier to the television over the alternate interface in response to receiving a polling message from the television over the standard HDMI CEC interface.

10. The method of claim 8, wherein the module identifier is a physical address provided by the television to the module over the standard HDMI CEC interface as a unique identifier of the module that the television uses to distinguish the module from other devices.

11. The method of claim 8, wherein prior to the television and the module transmitting CEC commands over the alternate interface, further comprising:
the television requesting a key from the module; and
only permitting the module to communicate CEC commands with the television over the alternate interface if the key matches the module identifier earlier provided.

12. The method of claim 8, wherein prior to the television and the module transmitting CEC commands over the alternate interface, further comprising:
the television and the module exchanging keys; and
the television only permitting communication with the module of CEC commands over the alternate interface if the keys exchanged between the television and module match.